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Waste Heat Recovery Questions

by TheBigBiscuit
Tags: heat, recovery, waste
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Nov10-12, 11:34 AM
P: 4
Hello, I'm new to these forums and hoping I can get some help with a project I'm undertaking in college. The project is to model a waste heat recovery system using an Organic Rankine Cycle (ORC). What I'm currently looking at is my waste heat source (exhaust gas from a natural gas engine). The parameters I'm considered with at present are the exhaust gas temperature and the specific heat of the exhaust gas.
Searching these parameters on the internet provisionally, I seem to be getting exhaust gas temperatures of approximately 1000 Kelvin for a 1.5 MW MAN gas powered engine, and specific heat seems to be between 1 - 1.3 kJ/kgK.
However these sources aren't as reliable as I'd like (not that they aren't accurate, but I'd like a bit more concrete proof or references if that's possible).
Any help would be greatly appreciated as I haven't looked at the gas engine side of the project in more detail as it's only the exhaust port of this that concerns the ORC, so it's likely I'm going about it the wrong way.
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Nov14-12, 03:39 PM
P: 661
You can perfectly check the composition of the exhaust gas and add the heat capacity of the constituents. H2O will increase it over N2. In the maximum case, all O2 burns CH4.
Nov15-12, 12:27 PM
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P: 2,793
450 to 550 deg C, with a Cp of 1.1 kJ/kg.K in the stack would be a good starting point for a lean burn engine.

Nov16-12, 03:52 AM
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Waste Heat Recovery Questions

TheBigBiscuit, Welcome to Physics Forums!

There may be a process in nature that might apply to your project. May I suggest that you have a look at how birds in frigid climates use a countercurrent heat exchanger between blood vessels in their legs to keep heat concentrated within their bodies? You may be surprised to discover how often some variation of this process is used by modern industry.

Nov17-12, 09:51 AM
P: 4
Thanks for taking time to reply. It's given me some food for thought. I may need to get back to ye at some point but thanks very much for this base.

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